I would say that the life of Billie Holiday is one where adversity is a constant presence.  The fact that she was raped and violated, both before and during her practice as a prostitute would demonstrate the idea of dealing with adversity.  In her experiences of Northern discrimination, which was covert and hidden, and its Southern counterpart, which was more overt, she faced adversity.  In having doors closed to her because of her race and her lack of wealth, another set of adversity was faced.  Finally, the dependency on drug use would constitute as another set of challenges that needed to be faced were present.  As indicated in much of her music, Holiday had many reasons to be a one who "sings the blues."